Solution of day 18-q1 in cpp #396

Author: Tech-neophyte

Day 18/q1: Maximum Difference Between Node and Ancestor/Tech-neophyte--c.md

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+## Approach:
+<br /> 1. Using dfs find the max value node and min value node in each branch and calculate their diffence.
+<br /> 2. Return the max difference. 
+## Code:
+```
+/**
+ * Definition for a binary tree node.
+ * struct TreeNode {
+ *     int val;
+ *     TreeNode *left;
+ *     TreeNode *right;
+ *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
+ *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
+ * };
+ */
+class Solution {
+public:
+    int maxAncestorDiff(TreeNode* root) {
+       return dfs(root,root->val,root->val);
+    }
+    int dfs(TreeNode* root,int mini,int maxx){
+        if (root==NULL){
+            return maxx-mini;
+        }
+        mini = std::min(mini, root->val);
+        maxx = std::max(maxx, root->val);
+        int left_diff = dfs(root->left, mini, maxx);
+        int right_diff = dfs(root->right, mini, maxx);
+        return std::max(left_diff, right_diff);
+    }
+};
+```